1. Field of the Invention
The present invention relates to a device for securing a part to a chassis and, in particular, to a device for securing a pinch roller support arm to a chassis of a magnetic tape apparatus.
2. Description of the Related Art
Here, description will be given below of an example of a conventional magnetic tape apparatus with reference to FIG. 6. In particular, in FIG. 6, reference numeral 1 designates a tape cassette which includes a supply reel 1a and a take-up reel 1b; 2, movable tape guide posts which are used to draw out a magnetic tape T from the tape cassette 1 and wind it onto a head cylinder 3; 4, a full erase head; 5, an audio erase head; 6, an audio/control head; 7, fixed tape guide posts; 8, a back tension post; 9, a capstan; and 10, a pinch roller support mechanism which includes a support arm 12 pivotally and rotatably supported on a support shaft 11, while a pinch roller 13 is pivotally mounted on one end portion of the support arm 12 and a cam pin 14 provided on the other end portion of the support arm 12 is fitted into a cam groove 15a formed in a rotary cam 15. Further, reference numeral 16 designates positioning projections which are respectively provided in a tape cassette placement position on a chassis 17.
In the above-mentioned conventional structure, to record and reproduce, the tape cassette 1 is fitted with the positioning projections 16 to thereby fix the tape cassette 1 at the tape cassette placement position on the chassis 17; after then, the magnetic tape T is drawn out from the tape cassette 1 and wound around the head cylinder 3 using the movable tape guide posts 2 and, at the same time, by rotating the rotary cam 15 by a given angle, the support arm 12 is rotated, so that the pinch roller 13 is pressed against the capstan 9 through the magnetic tape T, and by driving to rotate the capstan 9, the magnetic tape T is caused to run.
The support arm 12, as shown in FIGS. 7 and 8, includes a main arm portion 12a which is formed in a substantial U shape by sheet metal bending working, and an auxiliary arm portion 12b assembled in the main arm portion 12a. The pinch roller 13 is pivotally and rotatably mounted on the leading end portion of the main arm portion 12a, the cam pin 14 is projectingly provided on the leading end portion of the auxiliary arm portion 12b, through-holes 18 and 19 respectively formed in the main arm portion 12a and auxiliary arm portion 12b concentrically therewith are rotatably fitted with the support shaft 11, and the both end portions of a spring 20, which is assembled in the auxiliary arm portion 12b and is fitted with the outside of the support shaft 11, are respectively engaged with the main arm portion 12a and auxiliary arm portion 12b, so that the pinch roller 13 can be energized toward the capstan 9.
Conventionally, the support shaft 11 is secured to the chassis 17 by a nut 21 which can be threadedly engaged with the lower end portion of the support shaft 11, while a removal preventive washer 22 is fitted into a groove 11a which is formed in the upper end portion of the support shaft 11.
In the above-mentioned conventional structure, in order to prevent the support arm 12 from being removed from the support shaft 11, the removal preventive washer 22 is fitted into the groove 11a formed in the upper end portion of the support shaft 11. However, with use of this structure, the number of parts increases by an amount corresponding to the use of the removal preventive washer 22. Also, as described above, the groove 11a is formed in the support shaft 11 and the removal preventive washer 22 is fitted into the groove 11a to thereby secure the support arm 12 to the chassis 17. However, this securing operation takes time and labor, resulting in the increased production cost.